Gas turbines are well known and included, for example, in various power generation equipment and aircraft engines. Gas turbines typically have a gas path which can be subject to undesirable gas leakage, either into or out of the gas path, from an area of higher pressure to an area of lower pressure.
For example, leakage can occur through gaps between gas turbine subassemblies (e.g., through gaps between the combustor and the turbine) and/or through gaps between the components that make up a gas turbine subassembly (e.g., through gaps between combustor casing segments) which have surfaces of different shapes, can suffer from assembly misalignment, and undergo vibration. Moreover, components typically experience different hot gas flow and thus will typically undergo different thermal growths.
Such leakage is undesirable for a variety of reasons, including the fact that it can lower the efficiency of the gas turbine (leading to increased fuel costs) and/or require an increase in burn temperature to maintain a power level (leading to increased pollution).
Leaf seals made of metal have been used to reduce such leakage, though such seals have been found to leak an amount sufficient to increase fuel costs and/or increase pollution.
Alternative seals using cloth layers formed of wire mesh and variously disposed on opposite sides of a foil layer or metal sheet have also been used, as shown, for example, in U.S. Pat. Nos. 5,509,669, 5,586,773, 5,657,998 and 5,934,687.
U.S. Pat. No. 5,509,669, for example, discloses various seals with weld beads permeating the cloth layers and attaching to the foil layer and/or with the cloth layers generally enclosing the foil layer but leaving an edge of the foil layer exposed.
U.S. Pat. No. 5,586,773 discloses a particular cloth structure for such seals in which particular dimensions of center-to-center spacing and wire diameters are used whereby, in effect, the wires of at least one of the warp or weft wires would generally have significant spacing therebetween.
U.S. Pat. No. 5,657,998 also discloses seals in which cloth mesh layers are disposed on opposite sides of a foil layer (or layers), with the cloth layers also being wrapped around the edges of the foil layer(s). The cloth layers are spot welded on the foil layer (or in some instances having brackets are secured by a compressive fit).
U.S. Pat. No. 5,934,687 similarly discloses seals with cloth mesh layers on opposite sides of a metal sheet, with the metal sheet extending beyond the cloth on opposite edges to form curved portions having longitudinally extending portions which are equidistantly above and below the cloth layers. The cloth layers are spot or seam welded on opposite sides of the metal sheet.
The present invention is directed to providing a seal against gas leakage in gas turbines which not only reliably provides suitable sealing against undesirable leakage, but also allows use of manufacturing processes which are easy to use, inexpensive, and provide reliable, consistent seals.
Other objects, features, and advantages of the invention will become apparent from a review of the entire specification, including the appended claims and drawings.